Compare Loft Conversion Quotes: How Many Should You Get? (2026)
The right number is three. Two leaves you guessing whether the lower one is a bargain or a corner-cutter; five or more wastes weeks and rarely changes the picture. Three quotes reveal the genuine market rate, expose an outlier in either direction, and give you negotiating leverage. The catch: a quote is only comparable if every builder priced the same written specification — same dormer size, same steels, same staircase, same finish.
Comparing loft quotes — the short answer
- Get 3 quotes — the sweet spot between confidence and wasted time.
- Issue one written brief so every builder prices the same scope.
- Compare the spec, not the headline: steels, insulation, staircase and finish vary hugely.
- Expect a spread of 15–25% between the lowest and highest fair quote.
- Be wary of the cheapest if it is more than ~15% below the others — something is usually missing.
A quote that is dramatically lower nearly always excludes something the others included — steels, Building Regs fees, the staircase, or making good. The goal of comparison is not to find the cheapest number; it is to find the best value for an identical, fully-specified job. Knowing the typical loft conversion cost first helps you judge whether all three quotes sit in the right ballpark.
What Every Quote Must Itemise
Before you compare totals, confirm all three quotes include each line below. A missing line is where the “cheap” quote hides its real cost.
Tip: put your brief in writing (dormer dimensions, room use, finish level) and send the identical document to all three builders. That one step makes the totals genuinely comparable.
Quotes to Walk Away From
No written, itemised quote
A figure scribbled on the back of a card is not a quote. Insist on a written, line-by-line breakdown you can compare.
Large upfront deposit
More than 10–15% before work starts is a warning sign. Reputable builders use staged payments tied to milestones.
No insurance or memberships
No public liability, no FMB/CIOB membership and no references? Walk away — there is no recourse if it goes wrong.
Suspiciously cheap
More than ~15% under the others usually means an exclusion you'll pay for later as a “variation”.
Common Questions
Related Guides
More compare, cost and planning guides for your loft project.
Get 3 Free Loft Conversion Quotes
BestBuilders sends one brief to 3 vetted loft specialists so every quote prices the same scope — the like-for-like comparison this guide recommends, done for you. You can also compare the average cost by loft conversion type before you brief them.